The hedonic treadmill, also known as hedonic adaptation, is the observed tendency of humans to quickly return to a relatively stable level of happiness despite major positive or negative events or life changes.According to this theory, as a person makes more money, expectations and desires rise in tandem, which results in no permanent gain in happiness. and Donald T. Campbell coined the term in their essay "Hedonic Relativism and Planning the Good Society" (1971). The hedonic treadmill viewpoint suggests that wealth does not increase the level of happiness.